Jim Michalak's Boat Designs

(15JUN98) This issue will show how I lay out the design of the pivoting
leeboards that I use. In the 1July issue I hope hope to start a
discussion about sails that will last a few issues, ending with how I
have been making polytarp lugsails of late.

NEAT WEB SITE ALERT1...Click on over to
Dave Carnell
and sit down for a good read. It seems like I've known Dave forever. I
recall reading his stuff in Boatbuilder, Small Boat Journal, and The
Instant Boatbuilder way back when I first got started making boats.
Dave is the keeper of the Simmons Sea Skiff plans and has developed the
"$200 Sailboat". Also on his page are essays on buying and using epoxy
(he's a retired chemical engineer) and treating wood rot with
chemicals. Dave also sells Matsushita thin kerf carbide saw blades, the
blade that made my AF4.

Left:

HERB McLEOD'S AF3

Contents:

Contact info:

PIVOTING LEEBOARD DESIGN

This is a pretty easy writing assignment for me. I put a pivoting
leeboard on my Bolger Jinni back in 1982. At the time I thought I had
invented the thing until I saw Jim Huxford's Bolger Otter which
apparently had been built in the mid '70's. That boat had TWO pivoting
leeboards just like I had used. But these boards are braced to take
loads in all directions (so in fact they aren't really "lee" boards)
and there is no need to have two, one will do it all. For me the germ
of the idea came from Bolger's pivoting leeboards that appeared on his
Cynthia J and again on his original Dovekie. Those boards bolted
directly to the side of the boat. All I did was to stand the board off
the side a bit with a stick at the pivot point and contain the top of
the board in a slotted guard. Those two guards provide the reaction
points that allow the single board to be braced to take forces in all
directions and operate on all tacks. In most ways these are pivoting
leeboards are just like the usual centerboard mounted outside of the
hull. I quickly learned that an "eye" mounted on the top edge of the
board was important in that it provided a lug for attaching a lanyard
and, just as important, gives you a visual clue to the position of the
board. (My first attempt just had a radiused top edge. It looked the
same from the cockpit at all board positions and I never knew the
actual position without peeking over the side at the board, very
difficult to do on a small boat.) Anyway, here are the basics:

SIZE....

Leeboard size was discussed two issues ago. If you make the immersed
area of the board about 5% of the sail area you will be in the right
ballpark.

SHAPE...

Shape was discussed in the last issue. If you make the immersed board
about twice as long as wide you will have an aspect ratio of 4 and that
is pretty good for overall performance.

MOUNTING POSITION...

Here is where the leeboard differs greatly from a centerboard or
daggerboard. A LEEBOARD MUST BE MOUNTED AT THE WIDEST POINT OF THE HULL
TO BE IN FLOW PARALLEL TO THE HULL'S MOTION. If you are using one on a
slab sided scow you might have some options in this regard, but for a
normal pointy ended boat, it can only go in one spot.

Most folks won't mind placing the board at the hull's widest point. But
remember: THE SAIL AREA MUST BE BALANCED AROUND THE LEEBOARD AREA. So
you can't go around moving the mast or changing sail layouts without
taking this into account. There isn't much room for variation here,
especially with a narrow leeboard. Moving the sail forward a few inches
will make for lee helm (release the tiller and the boat heads downwind
on its own). Moving the sail aft a few inches will make for more
weather helm (release the tiller and the boat heads into the wind). SO
THE SAIL AREA MUST BE CENTERED OVER THE WIDEST POINT OF THE HULL. You
can't treat them separately.

Knowing the size shape and position of the leeboard you can draw it on
the side view of your hull. Check to see that isn't wider than the hull
is deep. If it is, you won't be able to pivot it up so that the
grounded boat will rest on the hull bottom and not on the leeboard.

SUPPORTS...

The leeboard supports, which I call the guards, need to be spaced apart
a fair amount to handle the loads introduced by the board. The farther
apart they are spaced, the more effective they are at sharing the loads
of the leeboard. If the guards get quite close together, they probably
won't always be strong enough and having the leeboard break loose will
ruin your day. Here's is a figure that demonstrates the effect:

The numbers used in the example might be pretty typical of a small
sailer. With one exception: consider a situation where a 200 pound
skipper is trying to right a capsized boat by stepping on the tip of
the leeboard. Then the loads will be much higher than shown. To put it
all into perspective, a typical cheap 1/4" bolt might handle 2000
pounds of tension and a 1/2" bolt maybe 9000 pounds.

PIVOT POINT....

About all that's left to do now is to find a pivot point that will
allow the leeboard to retract fully under the upper guard. Here is a
way that works well for the type of board I like to use which extends
straight up and down when lowered. Draw a line as shown in the figure
below starting where the trailing edge of the lowered leeboard meets
the bottom surface of the top guard, extend down at a 45 degree angle.
Where that line crosses the center of the lower guard is where the
pivot bolt needs to be mounted. I try to arrange things such that the
bolt falls about 1/3 to 1/2 of the way aft from the leading edge.

HOISTING LANYARD....

I've found that if the board has just the right amount of friction in
the guards (by adjusting the pivot bolt) it will stay down until it
hits something. If it hits something it will usually float up about 75%
of the way and stay, still providing some lateral area. Then if you
yank it down again, you are back in business until you hit the next
thing. If it is a shallow shore you are approaching you just let it
continue to come up until the boat is beached. I attach a lanyard to
the eye on the aft top edge of the board for yanking it down. I don't
cleat off the lanyard. I've never ballasted the board to sink although
some have tried that. I've never used a shock cord to hold it down
although some have tried that. I've never used a second lanyard to
hoist the board up although some have tried that.

OPERATION....

So the operation of the leeboard is quite simple as you see. It's
mostly like using a regular centerboard. When sailing anywhere but
downwind the board stays all the way down. When sailing downwind, I
usually leave the board down (usually the boat will steer better)
although at times it will swing up because it will have a fair amount
of drag and no side force to produce friction to hold it down. If so,
I'll leave it up but one must remember to yank it down again prior to
turning from the downwind run. If it ever hits something it will pop
up. Yank it back down. That's it!

NEXT TIME....

I'd like to start the topic of sails. This will most likely take a fair
amount of time. I might have to split it up with other topics to make
it more palatable and to give me time to figure out what to say.

Viola22

SAILING SHARPIE, 22' X 7'', 2200 POUNDS EMPTY

Someday I may get to put my full catalog on the net. For now I'll put
one design in each issue.

Viola22

Viola22 is a cabin sharpie: a handy cruiser suitable for a solo sailor
out maybe a week, or for duet out for a couple of days (I almost said a
weekend but mid-week boating is usually a lot more satisfying). Compare
Viola22 to a Catalina 22 which is something like the standard in
trailer-cruisers. They can be bought for about $3000 which about what
the Viola would cost to build if you watched your costs. Many older
Catalinas aren't really worn out at except for sun chalk. They are much
harder to rig than the Viola and draw a lot more water, even with their
keels swung up. They will sail better in rough conditions, but they
could never be dry-shoe beached as the Viola could. I'd say for solo
boating from a trailer the Viola would be a much beter choice. Compare
to a San Juan 21, which might sell used for $2000 on the trailer. The
San Juan will beach and trailer and launch similar to the Viola but
won't have the living quarters..

The living quarters of Viola are very good for her size. The main sleep
room is 6-1/2' long and almost 6' wide, plenty for two. There's a hatch
in its front for ventilation and setting the main in security. AFt of
the sleep room is a 3' long by 6' wide utility room. Use it as a
bathroom and kitchen and you can see that the sleep room needn't get
too cluttered with those necessities. Another advantage to this set up
is that the bedding shouldn't get wet everytime the main hatch is
opened or when someone strips off some wet clothing. Aft of the cabin
is a large flat cockpit with great storage underneath which is
accessible from both the cockpit and from the cabin. One trip on a
Micro will show you what a wonderful setup this is. Best of all, this
type of deck is very quick and easy to build. Aft of the cockpit is a
slop well meant to store the motor gear. There's another slop well in
the bow which is great for muddy anchors.

Construction is of straight forward nail-and-glue jigless plywood
needing no lofting or jigs. The plywood bill looks like twelve sheets
of 3/8", ten sheets of 1/2" (mostly for the double planked bottom) and
one sheet of 3/4" for the leeboard. Ballast is 600 pounds of steel bars
bolted to the bulkheads inside.

Prototype News

Some of you may know that in addition to the one buck catalog which now
contains 20 "done" boats, I offer another catalog of 20 unbuilt
prototypes. The buck catalog has on its last page a list and brief
description of the boats currently in the Catalog of Prototypes. That
catalog also contains some articles that I wrote for Messing About In
Boats and Boatbuilder magazines. The Catalog of Prototypes costs $3.
The both together amount to 50 pages for $4, an offer you may have seen
in Woodenboat ads. (If you order a catalog from an internet page you
might state that in your letter so I can get an idea of how effective
this medium is.) Payment must be in US funds. The banks here won't
accept anything else. (I've got a little stash of foreign currancy that
I can admire but not spend.) I'm way too small for credit cards.

Anyway..... Anytime a design from the Catalog of Prototypes starts
getting built I pull it and replace it with another prototype. So that
boat goes into limbo until the builder finishes and sends a test report
and a photo. Here are some boats in that catagory (although I been
leaving most in the prototypes catalog).

Sportdory: Dave Burdecki has his boat structually complete. He needs to
sand and paint and whittle out a set of oars. I think he may be also
finishing a Bolger Pirogue at the saime time. I know that sounds like a
lot of boats but it's all relative. We had a fellow show up at our
September messabout in Bloomington, In. a few years ago who claimed to
have owned 51 boats "not counting canoes"! You can check out John
Bell's Sportdory progress by clicking here .

Skat - the prototype Skat builder is Roger Palaski. Up until now he was
a mystery man know to me only as "Roger", his Skat plans bought for him
by someone else. Then I find out he has his own web page with the Skat
construction photos on it! Skat is a small somewhat traditional 12' cat
boat with a gaff rig. Even has a centerboard, the only boat I've ever
designed with one! See Roger's progress by clicking here.

The Way Up North AF3 project by Herb McLeod is shown completed up in
lead photo. It's not in the prototypes catalog anymore. Here's another
view: